The UK has condemned Bashar Assad's use of chlorine in Syria as an "outrage" after the international watchdog found chemical weapons had continued to be used in the conflict.

The Organisation for the Prohibition of Chemical Weapons (OPCW) found that a toxic substance, which was almost certainly chlorine, was used "systematically and repeatedly" in attacks on villages in northern Syria earlier this year.

The report by a fact-finding mission it sent to Syria does not apportion blame for the chlorine attacks on three villages, but Foreign Secretary Philip Hammond said there was "little doubt as to the Assad regime's culpability".

He said the UN Security Council should consider the report's findings and said the UK was consulting with international allies about the situation.

Mr Hammond said: "The findings of the latest OPCW report corroborate allegations that the Assad regime is continuing to use chemical weapons in Syria, in violation of the Chemical Weapons Convention.

"The systematic and repeated use of chlorine in northern Syria and the consistent reports from witnesses of the presence of helicopters at the times of the attacks leave little doubt as to the Assad regime's culpability.

"That the Assad regime continues to commit such atrocities against the people of Syria is an outrage. The regime's horrific attacks on its own civilians with chemical as well as conventional weapons further highlight Assad's disregard for international legal obligations, human rights and basic humanity.

"It is essential that the perpetrators of these crimes, and the other atrocities committed in Syria, are held to account. The UN Security Council must consider the report's findings. We are consulting with international partners on the best course of action."